Evidence-based knowledge creation on orthodontic mini-implants: ‘Why we know so little’

Orthodontic mini-implants (OMIs) are used as anchorage devices to counteract the reciprocal forces of orthodontic tooth movement. The 5 systematic reviews and 2 critical appraisals included in this thesis created evidence-based knowledge on a variety of questions on these devices such as (1) their success rates; (2) their effectiveness; (3) the adverse effects of using OMIs; (4) the role of insertion torque on the stability and the success of OMIs; (5) whether implants with root contact had higher insertion torque values than those without; and (6) the identification and quantification of barriers and facilitators to the implementation of OMIs.
Poor methodology and reporting, and multiple biases in the eligible studies of the systematic reviews downgraded the validity of many outcomes to low quality. Several cases of multiple publications of the same research data were identified. Meta-analyses could not be conducted in any of the 5 reviews. Responding of authors of eligible studies to questions by reviewers was mostly suboptimal. Overall 11 key points were presented why we still know so little on OMIs. The inclusion of non-randomized clinical studies, animal, cadaver, and artificial bone models in the systematic reviews in this thesis permitted the uncovering of numerous expected and unexpected findings. This thesis also addressed the importance of including multiple stakeholders to prioritize research questions on OMIs. Guidance was presented on how to improve research methods. Not considering the findings in this thesis could cause additional suffering of patients and animals and increase the production of avoidable research waste.